Sediment Control with Rice Straw Mat Covers from Sloping Sandy Fields - a Rainfall Simulation Study

Abstract

The Han River has been suffered from muddy runoff from sloping sandy fields in the alpine area in Korea. One of the utmost priorities of the government was to reduce the muddy runoff and sediment discharges and restore the water quality. The objective was to experimentally investigate the effect of rice straw mat cover on runoff, SS and sediment discharge from small laboratory plots that simulate the alpine area. The size of runoff plots was 1x1x0.5 m. Experimental treatments were rice straw mat cover of 0 (control), 3,000, 6,000 and 10,000 kg/ha, slope of 10 and 20%, and rainfall intensity of 30 and 60 mm/h, respectively. Runoff coefficient from the control runoff plots (0 kg/ha) was 55.0% and 70.4% (30 mm/h simulation) and were 66.1% and 85.3% (60 mm/h simulation) from 10% and 20% sloped-plots, respectively. Under 30 mm/h simulation, straw mat cover of 3,000 kg/ha reduced runoff by 98% and 82% from 10% and 20% plots, respectively. Under 60 mm/h simulation, when the soil was tightly covered, runoff coefficient decreased from 66.1% (control) to 1.3% (10% plot) and from 85.3% (control) to 16.6% (20% plot), respectively. Under 30 mm/h simulation, 3,000 kg/ha cover reduced sediment discharge 100% and 95.7% from 10% and 20% plots, respectively. Under 60 mm/h simulation, 6,000 kg/ha cover reduced sediment 91.2% and 94.3% from 10% and 20% plots, respectively. Suspended solids concentration from 0 kg/L (control plot) ranged from 1,450 to 2,930 mg/L. SS concentration from 3,000 kg/L plots were between 160 and 1,470 mg/L which meant the reduction of 89.0% and 49.8%, respectively. When the soil was tightly covered, the concentration further decreased to between 500 and 710 mg/L. It was concluded from a laboratory experiment that rice straw mat could be one of the agricultural BMPs that could control muddy runoff and sediment from sloping fields in alpine area in Korea. However, extensive field application tests were suggested to validate the laboratory test results before practical application.